Blow a kiss. Then pinch your lips into a thin line. Now alternate kiss and pinch several times a second for a pathetic, low-wattage human attempt at mimicking a disco clam.

Scuba divers call Ctenoides ales the disco or electric clam because the restless, curling lips of its mantle flash bright streaks. “It’s very vivid and very dramatic,” says Lindsey Dougherty of the University of California, Berkeley. She has made progress discovering how the poorly understood clams create a streak show. But that only deepens the puzzle of why.

This article is available only to subscribing members. Join the Society today or Log in.